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Using limiter and VGA in a receiver

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fanshuo

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can anybody give me some comparisons of these two options in receiver?
and why in GFSK zero-IF receiver limiter is not a good choice?( why those low frequency components in GFSK spectrum cause trouble?)

Thanks
 

Re: limiter and VGA

I think the VGA has larger linearity than limiter.
 

limiter and VGA

the VGA is need for any AGC loop and sure most of the receiveres need this AGC
about the limiter is used to eliminate any amplitude variations

i think they will both employed in FSK and GMSK

khouly
 

Re: limiter and VGA

Hi Khouly,
In the paper below it discussed the receiver architecture for GFSK. It rules out the zero-IF saying:
low frequency components of the GFSK spectrum produce harmonics that inside the signal bandwidth when converted to zero frequency. This degrades the SNR.

I do not quite understand
 

limiter and VGA

i checked the paper , it seems , that this is a result of high gain of the limiter , so it will distorted the signal , specially , there will be alot of nonlinearities

khouly
 

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    fanshuo

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limiter and VGA

but if the limiter is so nonlinear, it should also degrade the signal power due to its 3rd-order nonlinearity product in the low-IF structure
isn't it?
 

limiter and VGA

this also may happen

khouly
 

Re: limiter and VGA

because GFSK has considerable spectrum energy around DC, so about zero-IF architecture, limiter is not used for DC offset may degenerate the SNR, but in low-IF architecture ,limiter is suitable.
 

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